[GHC] #14194: ghci 8.0.2 panics

[GHC]

#14194: ghci 8.0.2 panics
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           Reporter:  jakubdaniel    |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:  x86_64         |   Type of failure:  None/Unknown
  (amd64)                            |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 I know it is rather hard to replicate but (I currently cannot check
 whether it still occurs in 8.0.2+):

 git clone https://github.com/jakubdaniel/expressions
 git clone https://github.com/jakubdaniel/expressions-z3
 hg clone https://bitbucket.org/jd823592/z3-haskell

 cd expressions-z3
 cabal sandbox init
 cabal sandbox add-source ../expression
 cabal sandbox add-source ../z3-haskell
 cabal install && cabal exec ghci

 λ> -- forget to :set -XTypeInType
 λ> :m Z3.Monad Data.Expression
 λ> -- forget to :m Data.Expression.Z3
 λ> evalZ3 $ astToString =<< toZ3 (forall [var "x" :: Var 'IntegralSort]
 (exists [var "y" :: Var 'IntegralSort] (var "x" .+. var "y" .=. cnst 0))
 :: Lia 'BooleanSort)

 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.2 for x86_64-unknown-linux):
         initTc: unsolved constraints
   WC {wc_insol =
         [W] toZ3_a4CL :: t_a4CK[tau:1] (CHoleCan: toZ3)
         [W] toZ3_a4Dx :: t_a4Dw[tau:1] (CHoleCan: toZ3)}

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14194>
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